Add an Init() method for client-only services

tracing/tracing.go

@@ -126,6 +126,11 @@ func initTracing(endpointAddr string) {
 	})
 }
 
+// Init tracing support, if not using WrapHandler.
+func Init() {
+	initTracing("")
+}
+
 // WrapTransport optionally wraps a http.RoundTripper with OpenCensus
 // tracing functionality, if it is globally enabled.
 func WrapTransport(t http.RoundTripper) http.RoundTripper {
@@ -136,7 +141,7 @@ func WrapTransport(t http.RoundTripper) http.RoundTripper {
 }
 
 // WrapHandler wraps a http.Handler with OpenCensus tracing
-// functionality, if globally enabled.
+// functionality, if globally enabled. Automatically calls Init().
 func WrapHandler(h http.Handler, endpointAddr string) http.Handler {
 	if Enabled {
 		initTracing(endpointAddr)